Field
Communication systems may benefit from a control channel for contention based transmission. For example, communication systems of the third generation partnership project (3GPP) long term evolution (LTE) and LTE-Advanced may use such control channels for contention based transmission. In particular, such control channels may be valuable with respect to LTE-based local area network (LTE-LAN).
Description of the Related Art
There are several scenarios for local area, for example indoor hotspot as shown in 3GPP technical report (TR) 36.814, where the area is mainly composed of multiple rooms. There also exists another scenario, for example an office enterprise, where the area is large work place. Neither the deployment of pico nor home eNode B (eNB) in current 3GPP is sufficient for this office enterprise scenario.
In 3GPP LTE, contention based random access is supported for uplink (UL) access and synchronization. From a physical layer perspective, the L1 random access procedure encompasses the transmission of random access preamble and random access response. A random access channel occupies 6 resource blocks in a subframe or set of consecutive subframes reserved for random access preamble transmissions. The eNodeB is not prohibited from scheduling data in the resource blocks reserved for random access channel preamble transmission.
Here the contention based UL transmission is used for random access, not for data transmission. Fixed 6 RBs are adopted in random access which is not suitable for data transmission. Furthermore, random access grant instead of ACK/NACK (A/N) is transmitted in response to random access.
Another approach is contention based UL transmission with a common/broadcast UL grant. In this approach the eNB broadcasts the contention based resources via a common UL grant to all UEs. When UE has data to send, UE may perform contention based transmission on the contention based resources indicated by the common UL grant.
However, the collision between UEs is very large since the available contention based resources are exactly the same. Moreover, the contention based resources are given by eNB and are common for all UEs while the data requirement for each UE may vary to large extent. Only the UE knows its own accurate buffer status. Furthermore, an UL grant is still needed.